This investigation concerns itself with those proteolytic forces and mediators released by proteolysis that may be involved in the growth, vascularization, and development of tumors. The role of the fibrinolysin and vasopeptide (kallikrein-kinin) systems in tumor tissue is under study. Both alkaline- and acid-dependent proteases have been isolated from solid and ascites forms of transplanted tumors. These proteases were shown to act on several kininogen sybstrates to form vasopeptides. This study is directed toward the isolation, purification, and characterization of these tumor (and fibroblast) proteases, and the formed kinins. A wide range of natural and synthetic proteases will be studied against these proteases to help clarify the kinetics and site(s) of action of the proteases. The inhibitors also will continue to be studied as potential chemotherapeutic agents in in vivo experimental tumor model systems. Immunofluorescent studies will help identify the specific cell localization of the proteases isolated and purified from the tumors. BIBLIOGRAPHIC REFERENCES: LeBlanc, P.P. and N. Back: Proteases during the Growth of Ehrlich Ascites Tumor. I. The Fibrinolysin System. J. National Cancer Inst. 54:881-886, 1975. LeBlanc, P.P. and N. Back: Proteases during the Growth of Ehrlich Ascites Tumor. II. The Kallikrein-Kinin System. J. National Cancer Inst. 54: 1107-1114, 1975.